1. Technical Field of the Invention
The invention relates to a rapid-action clamping cylinder.
2. Prior Art
A rapid-action clamping cylinder comprising a piston-operated pull-in nipple has already become known with the applicant's DE 101 23 270 A1. Disposed inside the housing of the rapid-action clamping device of that patent document was a lifting piston that was actuated in the central center recess of the rapid-action clamping cylinder such that is could pass through the locking device. The object of this measure was to move the lifting piston out of the central receiving aperture in the rapid-action clamping cylinder far enough to permit the pull-in nipple that was disposed on the underside of the workpiece pallet to be placed gently on top of the lifting piston, in order to thus be able to insert the pull-in nipple preferably without any damage into the interior of the rapid-action clamping cylinder.
In that embodiment, however, a full protection of the pull-in nipple against damage inside the center recess was not yet guaranteed. On one hand, a centering correspondence was lacking between the pull-in nipple and the upper side of the lifting piston because the two parts sat on each other only with flat stop faces in each case. On the other hand, the pull-in nipple was designed such that it was executed flat toward the receiving aperture so that an offset allowance of only 2.5 mm was allowed between the corresponding parts. The pull-in nipple could be offset only within the range of the offset allowance in order to still be able to enter into the central receiving aperture in the rapid-action clamping cylinder.
The offset allowance, however, was too small for most applications. It could therefore happen that the pull-in nipple—especially if it was fixed to heavy workpiece pallets—was offset by more than the offset allowance due to the weight of the workpiece pallet, and the nipple was lowered onto the cover of the rapid-action clamping cylinder offset from the receiving aperture. This meant a significant risk of damage. Additionally, the workpiece pallet had to be maneuvered with the hoisting equipment in such a way that the pull-in nipple would enter into the central receiving aperture of the rapid-action clamping cylinder.
If the pull-in nipple was placed down only slightly offset from the central receiving aperture in the rapid-action clamping cylinder, the lifting piston would be moved back into the central receiving aperture of the rapid-action clamping cylinder by a machine command during the continued insertion process, with the aim of lowering the pull-in nipple along with it. However, since the same sat on the receiving aperture of the rapid-action clamping cylinder slightly offset, it would drop into the central receiving aperture in a jerky movement. This was no longer a gentle insertion process. In the case of an undesired operational situation of this kind, it was possible that even the receiving aperture on the rapid-action clamping cylinder could become damaged.
Especially in the case of very large workpiece pallets with dimensions of up to 1 meter by 2 meters and a corresponding weight in the range of tons, it was difficult to lower pull-in nipples of this type by crane into the central receiving aperture in the rapid-action clamping cylinder without damage via a relatively small-tolerance inlet diameter. The insertion process was also made difficult, in particular because a visual monitoring was no longer easily possible in the case of workpiece pallets of that size. The pull-in nipples can be seen only with difficulty on the underside of the large workpiece pallet and a controlled insertion of the pull-in nipples into the barely visible insertion openings was not possible through visual monitoring.